The Rheology and Processing of Carbon Nanotubes for Polymer Composite Applications

A.W.K. Ma
University of Connecticut, US

Keywords: carbon nanotubes, rheology, processing, composite


Carbon nanotubes (CNTs) have a diameter on the nanometer scale and a length on the micrometer or even centimeter scale. The high-aspect-ratio (length to diameter ratio) of CNTs offers a unique competitive advantage for using CNTs as conductive fillers for polymers. Only a small CNT loading (typically < 0.1wt%) is needed to achieve conductive pathways and impart sufficient electrical conductivity for electrostatic dissipation applications. However, the high-aspect-ratio of CNTs also results in significant viscosity enhancements, posing a processing challenge. To this end, understanding the rheology of CNTs dispersed within a polymer matrix is critical to processing CNTs into functional materials in a scalable and controllable manner. The presentation will first highlight the landmark experimental observations in the rheology of two different classes of CNTs: CNTs that aggregate and CNTs that do not aggregate in flow. The shear and extensional flow behavior of these two classes of CNTs will be compared and contrasted. In the second part of the presentation, two different rheological models will be presented and discussed. These models connect the viscosity data with the orientation and the aggregation state of CNTs, offering insights into controlling the dispersion, alignment and the final properties of CNT polymer composites.